This invention is concerned with the detection of electromagnetic radiation.
The state of the art of infrared (IR) detectors, which are utilized in many scientific, medical, industrial, and defense applications, was significantly advanced with the introduction of impurity band conduction (IBC) devices. IBC devices, such as the Blocked Impurity Band (BIB) detector (see Petroff, et al., U.S. Pat. No. 4,568,960) and the Solid State Photomultiplier or SSPM (see Petroff, et al., U.S. Pat. No. 4,586,068), were originally developed primarily for applications requiring long wavelength infrared (LWIR--approximately 5 to 30 micrometers) photon detection, which involves extrinsic photocarrier generation. BIB detectors exhibit improved performance compared to the extrinsic detectors which were previously known in the art. The high concentration of majority dopant atoms used in BIB detectors allows the fabrication of a thin detector with high quantum efficiency, reduced sensitivity to nuclear radiation, and none of the irregular electrical characteristics found in previous extrinsic photoconductor designs. The SSPM, whose design was based upon the improvements achieved by the BIB detector, is capable of continuously detecting single photons with wavelengths as long as 28 micrometers.
Impurity band conduction devices have thus made possible significant performance improvements in detector technology for the long wavelength infrared energy region of the spectrum. It would be particularly advantageous to extend this technology over the short wavelength portion of the electromagnetic spectrum, including near infrared, visible light, soft X-rays, and X-rays, i.e., radiation having wavelengths less than approximately 1 micron; at these wavelengths, the absorption of light in silicon occurs by an intrinsic mechanism.